1. Technological Field
Exemplary embodiments discussed herein relate to a data communication apparatus, a method for its network configuration, and a computer readable recording medium storing its program.
More particularly, the exemplary embodiments relate to a data communication apparatus that forms a virtual network configured on a physical IP network in a non-structural topology which is independent of data placement, a node within the virtual network that transmits data to its physically adjacent node, and a method for configuring a virtual network of the same.
2. Description of the Related Art
Recently, P2P (Peer to Peer/Personal to Personal) networks have received more attention. In the P2P network, computers do not have any distinct roles such as a server computer or a client computer and evenly communicate with each other. It is said that the P2P network model is strong in scalability and fault tolerance because data and the load are distributed. Various applications using the P2P network model have been developed. For example, there is Gnutella software which allows files to be shared and opened to the public over a plurality of terminals.
The Gnutella software logically configures the virtual network of non-structured topology, which is independent from data placement. A search of all files stored in every node takes place by distributing a search query to all nodes as each node transfers the search query to an adjacent node.
Therefore, searching requires that a large amount of messages be exchanged, and this causes a problem of increased traffic.
Gnutella software configures the virtual network without considering physical routing of the IP network. As a result of this, there are many cases where adjacent nodes in the virtual network are physically distanced, and this is one cause of the increased traffic.
There are some conventional methods to reduce the traffic of the physical network and to efficiently determine the virtual network topology. Japanese laid open patent JP2005-252596 describes technology that measures response time for connecting between peers. However, there is a problem that a determination of the adjacent node cannot be accurate, since the response time may largely change from the load condition of the peer or the communication line in this technology.
In the conventional P2P network configuration methods, there are the following problems.
If a virtual network is configured to have nearly the same shape as the physical network, useless messages may be transmitted. Although, the conventional method requires massive communication traffic to measure a physical distance between nodes, it is difficult to measure the physical distance accurately. Further, the operation of the conventional method is also complex.
When the node decides to participate in the virtual network, the node connects to an already-known node by using a method of querying a server (which still requires that the address of the server be inputted). Therefore, the user has to be aware of the virtual network when participating in the virtual network.
The performance of the conventional network decreases if there are not enough gatenodes. If there are many gatenodes, the communication load between gatenodes goes up.
Having a virtual network configuration similar to the physical network configuration means that a plurality of virtual network node groups are connected with a small number of lines, since the IP network connects to a plurality of networks via a router(s).
In addition, the virtual network, such as P2P network, is often composed of the terminal, and nodes frequently join the virtual network or secede from the virtual network. Therefore, since a gatenode which connects a plurality of virtual network node groups may secede from the virtual network, decoupling of the virtual network may easily occur.
It is better to have more gatenodes so that the virtual network can be stable against participation and secession of the node. However, there is a problem that the communication performance decreases when links to nodes out of the subnetwork increases.